Phase change ink or solid ink compositions are characterized by being solid at room temperature and molten at an elevated temperature at which the molten ink is applied to a substrate. Phase change ink compositions generally comprise an ink vehicle and a colorant, and can be used for ink jet printing.
Phase change ink or solid ink printers conventionally receive ink in a solid form, sometimes in the form of ink sticks. The ink sticks are typically inserted through an insertion opening of an ink loader for the printer and are moved by a feed mechanism and/or gravity toward a heater plate. The heater plate melts the phase change ink impinging on the plate into a liquid that is delivered to a print head assembly for jetting onto a recording medium. The recording medium is typically paper or a liquid layer supported by an intermediate imaging member, such as a metal drum or belt.
A print head assembly of a phase change ink printer typically includes one or more print heads each having a plurality of ink jets from which drops of melted phase change ink are ejected towards the recording medium. The ink jets of a print head receive the melted ink from an ink supply chamber, or manifold, in the print head which, in turn, receives ink from a source, such as a melted ink reservoir or an ink cartridge. Each ink jet includes a channel having one end connected to the ink supply manifold. The other end of the ink channel has an orifice, or nozzle, for ejecting drops of ink. The nozzles of the ink jets may be formed in an aperture, or nozzle plate that has openings corresponding to the nozzles of the ink jets. During operation, drop ejecting signals activate actuators in the ink jets to expel drops of fluid from the ink jet nozzles onto the recording medium. By selectively activating the actuators of the ink jets to eject drops as the recording medium and/or print head assembly are moved relative to each other, the deposited drops can be precisely patterned to form particular text and graphic images on the recording medium.
Solid inks containing organic pigments and dyes or a pigment/dispersant package can show poor drooling behavior and unacceptable face plate staining on the ink jet print head. Attempts to improve drooling performance in solid inks have included changing pigments, changing dispersants, and using various synergists with the pigment to enable dispersion stabilization. Compounds available off the shelf to address this drooling and staining problem have shown an undesirably strong gelling behavior in solid ink. Certain acidic compounds, such as sodium dodecylbenzene sulfonic acid (DDBSA), have been incorporated into pigmented inks but did not improve drool performance.
There remains a need for improved phase change ink compositions that can provide improved drooling and staining characteristics. There further remains a need for green or bio-renewable additives for pigmented solid ink compositions that can provide improved face plate drooling and staining characteristics.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.